Philippine presidential front-runner Ferdinand Marcos Jr. and incumbent Vice President Leni Robredo are in a two-cornered race to succeed President Rodrigo Duterte as the Southeast Asian country enters the final month of campaigning for the May 9 election.

Analysts expect a neck-and-neck battle similar to the 2016 vice presidential race between Marcos, the son of a former dictator and namesake, and Robredo, a human rights lawyer and opposition leader.

Ferdinand Marcos Jr. speaks during a rally as he campaigns for the presidency on Feb. 19, 2022, in Caloocan, Metro Manila, in the Philippines. (Getty/Kyodo)

In 2016, Robredo beat Marcos by over 260,000 votes. Marcos claimed he was cheated and filed an election protest, which the Supreme Court dismissed in 2021.

This time, there are a total of 10 official candidates for president, limited by the Constitution to a single six-year term.

Candidates are elected individually by 67.5 million registered voters.

On foreign policy, Marcos has expressed an eagerness to stay on friendly terms with both the United States and China, despite Beijing's militarization of outposts in areas disputed by Manila and other parties in the South China Sea.

Vice President Leni Robredo (R) takes part in a rally as she campaigns for the presidency on March 20, 2022 in Manila. (Getty/Kyodo)

Robredo wants to use the 2016 arbitral ruling on the South China Sea as leverage to encourage other Association of Southeast Asian Nations members to come up with a code of conduct in the sea to defuse tensions between Beijing and other claimants in the disputed waters.

China has overlapping claims with four ASEAN member states -- Brunei, Malaysia, the Philippines and Vietnam -- and Taiwan in the South China Sea, a strategic waterway through which over one-third of global trade passes.

Citing the latest Pulse Asia survey, Aries Arugay, a professor of political science at the University of the Philippines, said this period is crucial because Robredo is gaining momentum.

The opinion poll conducted March 17-21 showed Marcos' lead over Robredo had narrowed to a margin of 32 percentage points from 45 points in February.

"The house-to-house campaigning of Robredo supporters is phenomenal in that national candidates traditionally preferred to hold mass assemblies," Arugay said.

In 2016, Duterte, who started as a poll survey laggard, had a breakthrough also around the same time during the campaign period. Arugay said that was also the case for the late President Benigno Aquino III against his rivals in the 2010 election.

Duterte's daughter Sara, running for vice president under Marcos' ticket, has maintained a wide lead over her rivals.

Marcos' camp said the survey showed people's "unwavering trust" in the Marcos' heir, who is facing disqualification at the Commission on Election and controversy over his family's unpaid taxes.

Robredo's supporters began focusing on house-to-house campaigning to reach more voters in lower-income communities.

Despite the endorsement of Marcos by Duterte's ruling party, the president says he remains neutral.

Duterte refuses to endorse any candidate "except of course my daughter."

"I will vote for my daughter," he said.

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